Taking the contents of the article on faith, I think the point was that their customers were abusing the startup's service for phishing.

This would be analogous to, for example, AWS taking reddit offline because a user posted a phising link.

Nearly every web business which lets people put information on the web that others can see will face abuse issues at some point or the other - and cutting off a business and its legitimate customers because of one client misusing the service does not inspire confidence.